1. Field of the Invention
The present invention relates to a position control server, an access point, and a call control server, and more particularly to a position managing server that manages a position of a mobile terminal in an internet protocol (IP) telephone service, an access point, and a call control server.
2. Description of the Related Art
In recent years, IP telephone services have been prevailing. In a common IP telephone system, IP telephones are fixed terminals similarly to an ordinary wired subscriber telephone service. A call control server that controls calls is usually called “SIP server” because the server utilizes a session initiation protocol.
An SIP server utilizes an SIP uniform resource indicator (SIP-URI) as an identifier of a user. However, the position of a user, that is, the installation site of an IP telephone, can not be identified from the SIP-URI. When position information of an IP telephone needs to be utilized at the time of a call process, a table in which the SIP-URI and the installation site are correlated in a static relation is required. However, because this approach only statically manages the position of the IP telephone, this approach can support the case where the IP telephone does not move, however, this approach can not support the case where the telephone moves.
Wireless IP telephone systems using wireless local area networks (LANs) have started to be used as extension lines in companies. If wireless IP telephone services are offered not only inside the companies but also in public wireless LANs and ordinary houses by communication business entities (carriers), it will be possible for a user to use an IP telephone moving freely among a company, a public wireless LAN, and his/her home.
As a consolidated use of public communication networks and private communication networks, the following communication system is known. The communication system includes a mobile switching system (MSC), a first base station subsystem (BSS) having at least one base station (BTS) that communicates through an air interface using a mobile terminal (MS), and a second subsystem (wireless intranet office (WIO), BTS), that has at least one base transceiver station (BTS) that communicates with the mobile terminal (MS) through an air interface, and is accessible by a first group of mobile communication subscribers of the communication system (for example, Japanese Patent Application Laid-Open Publication No. 2002-507869).
However, as described above, dynamic management of the positions of terminals cannot be achieved in the conventional IP telephone system. Therefore, various problems arise when the service area of the wireless IP telephone service is expanded and when a user moves carrying a terminal. For example, in each of areas such as a company, a public wireless LAN, and home, the maximum number of terminals that can be connected at the same time is limited according to the environment such as a band. However, when a terminal can freely move among those areas, the SIP server can not recognize which area the terminal is making a call from with the SIP-URI, and therefore, it is impossible to limit the number of terminals to be connected at the same time from each of the areas.
When a terminal is connected through a LAN in a company or is connected through a public wireless LAN, the usage fee rate may be varied. However, the SIP server can not recognize the area from which a moving terminal is connected with the SIP-URI, and therefore, the usage fee can not be charged according to the usage fee rate corresponding to the location of the terminal. In addition, even if the terminal that has been connected in one area of one usage fee rate moves to another area of a different usage fee rate, the SIP server can not recognize the destination, and therefore, the usage fee can not be charged according to the location change.
To determine the position of a terminal using the IP address thereof can be contemplated as a means to cope with the location change of a terminal. However, generally, private IP addresses that are available only in the LAN within the company are used in companies. A private IP address is dynamically converted into a global IP address by an application level gateway (ALG) installed in a carrier network of the communication carriers. Therefore, the position of a terminal can not be uniquely identified with the IP address in such environment that private IP addresses are used.